Multistage pump



Jan. 1, 1929. 1,697,299

J. A. ZUBLIN l MULTISTAGE lPUMP 1 Fned Jan. s. 1924 -4 sheets-sheet 1 v Hrw/ways.

Jan; l, '1929.

J. A. ZUBLIN MULTISTAGE PUMP Filed Jan. 5, 1924 4 sheets-sheet 2 Hrw/mfg?. A

Jan. l, 1929. 1,697,299

A J. A. ZUBLIN MULTISTAGE PUMP Filed Jan. `5, 1924 4 sheds-sheet 4' 7 AAf/ r oo @1| l l 1i .ll

Patentecl- Jan. 1, 1929.

JOHN A. zUBLiN, oF Los ANGELES, CALIFORNIA.

MULTIsrAGE PUMP.

Application filed January 5, 1924. Serial No. 684,578.

My invention relates to pumps and is particularly applicable to oil well pumps.

Inthe art of pumping oil, it is sometimes necessary to raise the oil from great depths. In pumping oil wells, it is necessary to place the pump at or near the bottom of the well, the plunger being actuated by a string of pump rods passing downwardly through the tubing. Invery deep wells the pressures encountered are high and the strains on the rods and the pump are very great. The ordinary forms of oil well pump used in shallow pumping are inadequate for deep service and it is an object of my invention to provide a pump which is especially adapted for' deep well service.

The strains imposed on the pump arise from two sources. There is, iirst, the constant static pressure due to the weight of the column of oil which must be lifted, and, second, a variable dynamic pressure due to the acceleration of this column of oil for each stroke of the pump. The maximum values of the latter depend upon the depth, speed of pump and other variables. l

vDue to conditions in the formations surrounding an oil well, it is almost always imi static.

possible for the pump to deliver full capacity and in many cases such pumps deliver less than ten per cent of their capacity. Where a single plunger pump is used, the full static pressure is on the plunger during the entire up stroke and for a considerable portion of the down stroke.. y When such a pump is piunping only ten per cent of capacity, the plunger carries full static load ninety-five per cent of the time, that is, on the entire up stroke, and ninety per cent of the down stroke. y

I have found that where the dynamic and the static pressures are both imposed on the same plunger in a deep well, it is extremely ditlicult to keep the plungers tight and it is an object of my invention to provide two plimgers, one of which takes the dynamic pressure and the other of which takes the It is also an expensive matter to withdraw such pumps for inspection or repair, and it is a :further object of my invention to provide auxiliary plungers which may be depended upon in the event the main plungers fail to hold the pressure.

I have found that there is tendency for silt to work in between the plunger and the inner wall of the pump barrel and that the presence of abrasive particles, such as silt, rapidly wears both the barrel and the plunger. If the plunger is longer than the stroke, there is a portion of the barrel that is never directly exposed to the oil, and abrasive matter tends to collect and adhere to this portion, rapidly wearing the barrel and plunger. It is, therefore, a further object of my invention to provide a plunger which is considerably shorter than the stroke so that any abrasive material lodging between the plunger and barrel has a chance to work out, the entire wall of the barrel thus being exposed to, and washed and lubricated bythe oil.

It is a further object'of my invention to provide a plurality of short plungers which have some relative flexibility so that they canaccommodate themselves to barrels that are slightly out of alignment.

Further objects and advantages will be made evident hereinafter.

Referring to the drawings which are for illustrative purposes only,

Fig. l is a section through the upper vportionof an oil well pump embodying my invention.

Fig. 2 is a section through the central por- 'i tion of the same pump.

Fig. 3 is a section through the lower portion of the same pump.

Fig. t is a section on a by the line L-a of Fig. 3.

Fig. 5 is a section on a plane represented by the line 5-5 of Fig. 2.

Fig. 6 is a diagram-representing the pressure on each plunger during the stroke of the pump.

Fig. 7 is a diagram representing the static pressure for different depths of su mergence of the pump. Y

Fig. 8 is a section through an oil well in which my invention is installed.

Fig. 9 is a section through a portion of an alternative form of pump'.

Fig. l0 is a similar section through the lower part of the same.l

Fig. ll is a view of a standing valve used with my invention.

In Figs. l to 5 inclusive, I show a two plunger pump which is the simplest form adapted to the practice of my invention.' In this form I employ a barrel 11y which is sus# pendedby a coupling 12 on thev tubing 13 of the well. The pump plun ers may slide directly in the barrel 11 but prefer to employ liners lll which may be replaced when worn plane represented and which fit inside the barrel 11. The liners are clamped between a lip on the coupling 12 and a similar lip 16 on a lower coupling 17 which connects the barrel 11 -with extension tubing 18. A central opening 19 is provided in the lower coupling 17, this opening having a conical seat 20 upon which a standing valve cage 21'is seated. The cage 21 also has a central opening 22 which may be closed by a steel ball 23. "Secured to the top of the standing valve cage 21 is a garbut rod 24 having an enlarged head 25.

The garbut rod 24 extends upwardly through an opening 30 in a lower quill 31, this opening being too small to allow the head to pass therethrough. The quill 31 is threaded on both ends and has an annular shoulder 32 near the upper end.

35 36, The

Threaded on the quill 31 is a spacer which is jammed against a lower seat which is also threaded on the quill 81.

. lower seat 36 has anupper conical surface 37 upon which a lower plunger 38 seats. The plunger 38 fits tightly inside the liner 14 and l its upper end fits upon alower guide 40.

7 VThe lower guide 40 Vhas a central threaded opening in which the lower quill 31 and a central quill 41 are threaded.

j The opening in the `quill 41 is large enough to allow the head 25 to pass freely lin and out of the quill. The lower'guidef40 also has openings 42 therethrough, so that oil can passfreely at all times from the interior of the plunger 38 to the space between the lower guide 40 and the liner 14.

Also threaded on the central quill 41 is a central seat 48 which has a conical upper suri i' tace 44, on which an upper plunger 5() seats.

The seat 43 is a duplicate of the seat 37 and the plunger 5O'is a duplicate of the plunger 3 8.` The plunger 50 slides on an upper guide 51'whichhas a central opening in which the central quill 41 and an upper quill 52 are threaded. The guide 51 is a duplicate oi the guide 40 and the quill 52 is a duplicate or the quill 31.- f

An upper seat 55 is also threaded on the i upper quill 52, being used as a lock nut to jam against the guide 51. The upper quill 52 is secured to standard pump rods by a coupling 61.

Itwill be knoted that each of the plungers,

with its associated guide, seat, and quill,

forms a unit which can readily be combined with one or more similar umts. In Figs. 1 to 5 inclusive, I show two such units and in l Fig. 8 I show four such units.

, The plungers are reciprocated through the pump rods 60 in any convenient manner as, for example, through a walking beam 65. The tubing lmay be suspended in the well,

. insidecasing 66 from a casing head 67.

, In the form of my invention shown in Figs. 9, 1 and 11, I employ the conventional type of ball valve now in use in the majority of in the enlarged 'The ends or' the rods 83 are lenlarged to form cages 86, inside which the balls 85 are coniined. The upper end of the upper rod may be secured by means not shown to a string of i pump rods. Screwed in the lower piston is a standing valve tamper 88 which iits overa 'uojection 89 on a standard standing valve 90, and by means of which the standing valve can be solidly seated.

In considering the operation of my invention, it is necessary to consider conditions in the well which may be illustrated by Fig. 7. In this ligurefI show a ldiagram of a well in combination with a pressure diagram. In the pressure diagram vertical distances represent the depth of the well and horizontal distances represent pressures. Thus the line AB represents depth and the line BC represents the static pressure at a standing valve 70 with the tubing 'full of oil. This pressure BG falls to Zero at the surface of the ground along the line CA. l

In considering the action of an oil well pump, it is necessary to bear in mind that oil in the average oil wellis quite an elastic fluid due to the presence of expansible gas therein. Suppose that thisgas content is ten per cent of the volume of fluid in the well, and suppose that the plunger 71 having the valve 72 has just completed its 'down stroke and is about to start up. At this instant the pressure on both sides of the plunger 71 is equal and may be represented by the line DE. As the pump starts up, the pressure on the upper side of the plunger falls' along the' line CA, since the oil is forced out of the tubing and the submergence is lessened. The pressure on the under side of the plunger also falls. It does not, however, fall to Zero as would be the casewere a non-expansible fluid, like water, being pumped. Due to the presence of gasfin the oil, the combined fluid expands so that the pressure falls inversely as the volume increases. This i'all in Ipriessure follows the line EP. Now if the' stroke be small, as for example ES, we find that' at the end of the stroke the pressure on the bottom of the plunger'is LK and the pressure on the top is LS, leaving the difference or KS as the eiective pressure. It will be noted that in the case of the submergence shown, this eiiective pressure is small. In the diagram we show similar pressure igured on'a gas volume of ten per cent for 5() per cent and 75 ,per centsubmergence.4 It is evident with these greater submergences the effective pressure for the same stroke becomes greater, this being of course due to the smaller volume of gas between the plunger 71 and the standing valve 70. The actual increase in effec,-

y' tive pressure with any increase in submergence for any given oil is, however, greater than that shown, since the greater the depth, the less th-e percentage of gas volume due to the increase in pressure, and the less the gas volume, the faster the pressure on the bottom of the plunger falls. Gbviously, therefore, any plunger, to be really effective, must operate close to the stan-ding valve 70.

In the diagram of Fig. 7, I have however neglected to consider dynamic pressure `due to the acceleration of the oil with each stroke of the pump. The effect of this may be understood from a consideration of Fig. 6, in which horizontal distances represent time and vertical distances representmovement or pressure. Thus MJ represents the time taken on the up stroke and J N the time taken on the down stroke. The movement of the plunger, if it be crank actuated, may be shown by a sine curve FG.

It is evident that acceleraton of the oil takes place only on the first half of the up stroke or from M to J, and were I dealing with a solid body, the pressure necessary to produce this acceleration would follow a line MQJ. But the pump rods are elastic and the fluid pumped is elastic and the dynamic pressures are retarded following a line MHS. It is evident that in a single act-ing pump, this force is acting only over a little more than a half of the time and that it may be nearly twice the magnitude of a steadily and uniformly applied force capable, if acting continuously, of lifting the same amount of oil. Since the tubing is made large for mechanical reasons, the velocity through the tubing is low an-d friction may be'neglected in considering the theory of operation.

I have found in the actual pumping of oil wells that this intermittently applied 'dynamic force may be greater than the static force, due to plain lift.

4Now in an ordinary pump the pressure on the plunger at any instant is the sum of the dynamic and static pressures at that instant.

The simultaneous closing action of the plungers or balls` leaves full dynamic pressure on the top plunger and full static pressure on the bot-tom. The intermediate plungers, if more than two plungers are used, are inactive unless the top or bottom plunger leaks, in which event the intermediate plungers take the load.

I am thus able, by a suitable arrangement of my pump, to cause the dynamic pressure to be taken wholly on the upper plunger and the static pressure to be taken on the lower plunger. This I may accomplish by making the distance between the seat 37 and the guide 40 slightly more than the distance between the seat 48 and the guide 51. This allows the upper plunger 50 a longer movement than the plunger 38.

On the down stroke of the pump, there is no unbalanced pressure-on these plungers l and they areV frictonally' retarded until pushed down by the guides 40 and 5l. When the up stroke starts, the lower plunger is therefore further from its seat thanthe up plunger moves before the lower plunger seats there is so slight an opportunity for eXpansion of the Huid below the upper plunger that the drop in pressure is negligible and the full static pressure of the well is' substantially vexerted on the lower plunger. The dynamic pressure at `this point is negligible due to the fact that yacceleration has not yet started. n V

By placing the lower plunger in such a position that it is close to the ball 23 at the lower end of its stroke, and thus providing a very small volume of oil between the lower plunger and the ball 23, I am able to provide a very rapid increase in volume of the space in which this oil is held and a consequent rapid drop in pressure on the bottom of the lower plunger, and consequently a high average effective pressure on this plunger.

By placing the upper plunger close to the llower plunger, I reduce the amount of fluid between the plungers to such an amount that there is substantially no dynamic load on the lower plunger, the whole of this load being imposed on the upper plunger.

By utilizing more than two plungers, I am able to provide reserve plungers that come into action only when the upper plungers fail.

By the peculiar construction employed and especially that shown in Fig. l to Fig. 6, I am able to provide only a few cubic inches of oil between the different plungers.

While I have described the top plunger as closing first, this is not absolutely necessary.

The plungers may lclose simultaneously or their time of closing may be regulated to dis tribute the load in any desired manner on the different plungers.

I have found that by the use of my invention, I am able to pump very deep wells and that the pump, when so used, will operate over long periods without attention.

I claim as my invention:

l. A pump for oil wells comprising: a barrel; two plungers fitting in said barrel directly adjacent to each other; and valve means associated with each plunger, one of said valve means being set to close before the other.

2. A pump for oil wells comprising: a barrel; two plungers fitting in said barrel directly adjacent to each other; and valve means associated with each plunger, the valve means associated with the upper plunger being set to close first.

- 3. In a deep well oil pump: a lower plunger; a lower seat for said plunger; a lower guide above and for said plunger and engaging said lower plunger only at the upper end thereof; an upper seat above said lower guide; an upper plunger above said upper seat; and an upper guide above and for said upper plunger and engaging said upper plunger only at the upper end thereof, the

distance betweensaid lower seat and saidlower guide being` greater than the distance between said upper seat and said upper guide.

4. In a deep well oil pump, the combination of: a plunger for taking the dynamic a lower plunger in said barrel; means for connecting said plungers; valve means upon the assembly of said plungers and said connecting means closing during an upward stroke of said plungers to trap a body of well liquid between said plungers at a pressure equal to a givenproportion of the fluid pressure imposed upon said upper plunger on said up stroke; and means whereby the relative pressure of said well fluid between said plungers on said up stroke may be controlled.

6. In a deep well pump, the combination of: a barrel; a piston in said barrel which includes an upper plunger and a lower plunger and means for connecting these together to form a well fluid passage enclosed by said barrel and adjacent ends of said plungers; primary valve means upon said piston admitting well fluid into said passage on the up stroke before said primary valve means closes; secondary valve means upon said pis ton discharging well fluid from said passage on the up stroke before said secondary valve means closes; and means for regulating the relative times of closing of said valve means.

7. A combination as in claim 5 in which said plungers are eXpansible.

8. A combination as in claim v6 in which said plungers are expansible.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 31st day of December, 1923.

JOHN A. ZUBLIN. 

